Powder Coating Specification: A Checklist for Engineers

The difference between a coating that performs and one that fails early is usually written before the first part is coated. A precise specification protects you in procurement, in production and in any warranty dispute. This checklist covers the fields every powder coating specification should include.

The Ten Fields Every Spec Needs

• Substrate material and surface condition, including castings or galvanized steel
• Pretreatment standard: blast grade, profile, and conversion coating
• Coating system: resin chemistry and any primer or topcoat layers
• Color reference: RAL, Pantone or approved physical sample
• Gloss level at the specified angle
• Dry film thickness as a minimum, with measurement method and locations
• Cure schedule matched to the part, not just the powder data sheet
• Performance tests: adhesion, impact, salt spray, UV and any special requirements
• Approvals and documentation: COA, RoHS, REACH, water-contact certificates
• Acceptance criteria: sample plan, tolerances and who approves

Writing Thickness and Test Clauses

Say what you will measure, where, and how many points. A typical clause reads: minimum 60 microns DFT on flat surfaces and edges, measured with a calibrated gauge per ISO 2360 or ASTM D7091, with three readings per part on a defined sample plan. Avoid average-only clauses, because they let thin edges pass.

Documentation That Survives Audits

• Batch COA with measured values, not just a statement of conformity
• Approved sample panel kept and signed for reference
• Incoming inspection records on your side
• Test reports for any guaranteed property, from an accredited lab where possible

Common Mistakes That Cost Money

• Specifying a color without a gloss level – the same RAL can look very different in matte and gloss
• Forgetting edge coverage on laser-cut and punched parts
• Using one spec for indoor and outdoor parts without separate clauses
• Accepting a data sheet as proof of performance without batch test records